Tuesday, 28 June 2011

Following on from my research on annual body clocks last week, I came across quite a number of papers associating the season of detection of breast cancer with survival rates.

A 7-year study that was published in 1983, looking at ~3000 female patients showed a peak of breast cancer symptoms in Spring, with a corresponding trough in the Autumn [1]. This has been verified in many other studies across the globe, showing tumour growth and aggression is higher in Spring.

Larger studies went on to determine a link between the survival rate of cancer patients and the seasons the tumour was detected and treatment began. One study of over a million cancer patients in the UK showed that a patient diagnosed in the Summer or Autumn had a greater chance of survival than if diagnosed in the Winter [2].

A smaller study, under 50 000 women, in Norway also confirmed that a Summer diagnosis increased the chance of survival by 10-15% over a Winter diagnosis [3]. This data was collected between 1964-1992 and looked at the differences in age and the region them women were living. Women under 50 that lived in a region with more sunlight had a better prognosis than those regions with less sunlight. However, although seasonal rhythms were detected, no regional differences were observed, in women over 50.

Women (under 50 years old) in Norway had a lower risk of dying from breast cancer within 3 years if their detection and treatment began in the Summer, in a region with most sunshine. (Porojnicu et al, 2007)

So, can sunlight improve survival rates of breast cancer? Or are there other factors, such as a higher number of infectious diseases around wintertime.

There is growing support that vitamin D, a chemical our body makes in response to sunlight, plays a role in survival against cancer [2]. Lab studies have shown that the products our body makes from vitamin D slow down cell growth [4]. Also, seasonality in cancers is more likely to be seen in women than in men, which is consistent with women being frequently reported of having lower vitamin D levels in winter.

One way to look at the link between vitamin D and cancer would be to look at cultures that eat more dietary vitamin D, or have a diet that changes the rate of vitamin D production. Drug companies are also looking into producing the products of vitamin D that may help cancer patients.

The link between vitamin D products and cancer survival still needs to be fully addressed. Until then, the advice is for women to check themselves monthly, and go out and enjoy the summer sunshine. (Don't forget the sunscreen!)

Tuesday, 21 June 2011

Today, the 21st of June, is the longest day of the year, commonly known as the Summer Solstice. The sun will be in the sky for 4 seconds longer than yesterday and 2 seconds longer than tomorrow. But more importantly, in the UK Summer has now officially started, and surprisingly we have blue skies and sunshine in London.

Blue skies in Greenwich at Summertime

I thought I’d take this opportunity to read up on and discuss whether our body has an annual clock, as well as a daily clock.

To measure the time of year, an animal can either know it is Winter, because the daylength (exposure to light) is short, or it can have an innate clock inside that measures one year. Or it can have both.

In some species annual clocks are very apparent: in Autumn birds begin to migrate to warmer climates, in Winter bears hibernate, in Spring lambs are born and in Summer we see our garden plants flourish.

There is much less research carried out on annual rhythms as opposed to daily rhythms. It takes scientists much longer to collect the data, and there are many variables that can cause any observed rhythms, which makes the data harder to interpret.

In humans it is especially tricky. Length of daytime is not the only thing that alters during the seasons. There are potential effects of temperature, climate, food availability, agricultural cycles, and holiday seasons, to name but a few.

One study has looked at the quality of embryos and sperm produced for IVF treatment in Iranians between June 2001 - June 2004, which included over 1000 treatment cycles [1]. They showed conception was much more likely during the Spring months of March-June. This time was also the best for quality of embryos and men had a higher sperm count. However, no changes were observed in egg number, sperm quality, and other factors.

Seasonal effect on number of successful pregnancies following IVF treatment in different seasons, (Vahidi et al, 2004)

Has electric lighting, and the ability to have as long or short a daylength as we like, disrupted our annual clock?

Another investigation published in 2004, examined the birth patterns in Spain between 1900-1978 [2]. Up until the 1960s there was a strong correlation between season and birth. However, when industrialization and subsequent changing in heating and lighting conditions was introduced the amplitude of this rhythm dropped: there wasn’t such a difference observed between different seasons.

The question whether humans still have, or if we ever had, an annual clock of changing biology and behaviour is still open for a lot of research and debate. Russell Foster, a researcher at Oxford, has written an interesting and in depth book on annual body clocks, which I would recommend to anyone who enjoys this topic.

Monday, 13 June 2011

Ever been camping and felt really sleepy and time for bed, only to discover its just 8pm?

How about staying up til 2am playing computer games (perhaps later?) because you didn't feel tired.

Do you struggle to get out of bed when the alarm clock rings in the morning?

Hitting the snooze button isn’t always a sign of laziness; sometimes our body clock becomes out of sync with the outside world. Electronic lighting, TVs and computer screens are often pinpointed as the culprits for this desynchronisation.

Light is one of the strongest time cues to tell your body it's daytime. Simply put: light in the morning wakes you up, dark in the evening helps you fall asleep. Although it's not always as simple as that. The type and amount of light matters too.

Our body clocks are most sensitive to blue light. There are specific photoreceptors in the eye, at the back of the retina, that detect light and signal this to the brain [1]. These photoreceptors are particularly sensitive to shortwave lengths, i.e, blue, light.

Short wavelengths of 420-480nm (blue light) are most efficient at resetting our body clocks.

The circadian system is important to our biology so other wavelengths of light can still reset our clocks, but they need to be brighter. If you don’t want to stay up all night avoid bright white lights in the evening [2].

The photoreceptors are not sensitive to short bursts of light, so a single bolt of lightning would not reset your clock; the light needs to hit the retina for several minutes. So a long trip to the bathroom in the middle of the night might trick your clock.

If you want to get a good night’s sleep, in the evening use dim lights with longer wavelengths (reds) of light. A few computer users have found using software like f.lux useful. This is a free software that colours your computer screen in a red hue in the evening and night time. This is good news for those of us who still want to play on the computer in the evenings, without keeping us up all night. It comes on automatically, however it's easy to turn off and on for doing colour sensitive photographic work.

I’ve joined 46 000+ others in “liking” f.lux on facebook. If you do try f.lux, let me know how you get on.

Tuesday, 7 June 2011

Summer is on its way, and for 1 in 3 of us this will mean hayfever too. I haven’t suffered from hayfever for a few years, although I do sneeze quite a lot throughout the year, and this is mainly when I wake up in the morning. It appears I’m not alone.

Two medical school students monitored the sneezing patterns of one of their classmates. The majority of their sneezes occurred at around 8.20am, and this shifted by 1 hour when daylight savings came on. After recording 118 sneezing episodes over the course of half a year, they admitted to their colleague what they had been up to and asked permission to publish their results [1].

A larger study of around 800 hayfever suffers has also showed that symptoms are most severe in the early morning. Around 60% suffered from sneezing, stuffy nose, blocked nose and runny nose when they woke up, and there was a clear daily rhythm of these symptoms [2].

Most hayfever sufferers show a daily peak in symptoms upon waking up (Adapted from Reinberg et al, 1988)

Hayfever symptoms are part of the immune system responding to an allergen, in most cases pollen. Histamine is one of the key chemicals produced by your body to communicate this response around the body. When the immune system is activated it produces a lot of histamine. Histamine interacts with the H1 receptor in the nose, causing inflammation to remove the allergen.

Antihistamine medication can relieve the symptoms of hayfever by reducing inflammation in the nose. However, the same H1 receptor that histamine interacts with is found in the posterior hypothalamus in the brain, where histamine plays another role in maintaining alertness. Early antihistamine medication often caused drowsiness by also interacting here.

It is often recommended to take antihistamines at night to counteract drowsiness during the day. If you are taking a once-a-day antihistamine tablet it is also advised to take it in the evening so the dose is being most effective in the morning when you wake up and it’s most needed [3].